Recently, with the improvement of living standards, people's concern about environmental beautification is gradually increased. In this regard, since dirt, leaves, gravel and the like (hereinafter, simply referred to as “refuse”), which are scattered on the street, defile the appearance of the street, it is necessary to frequently sweep them up.
If the refuse is introduced into and accumulates in a sewer pipe, the sewer pipe is likely to be clogged by the refuse. As a consequence, flow of sewage is obstructed, and, as a result of this, backflow of sewage may take place. Also, when compared to the case of sweeping refuse on the street, a great deal of costs are incurred upon removing the refuse after introduction thereof into the sewer pipe, whereby economic loss is caused.
It is the norm that street sweeping is conducted at dawn in order not to obstruct traffic flows. In the case that a sanitation engineer manually sweeps the street, a possibility of the sanitation engineer to be exposed to a traffic accident is increased. Therefore, it would be preferable that the sanitation engineer conducts a sweeping task while riding a vehicle which is equipped with a refuse collecting arrangement.
Referring to FIG. 5, there is shown a side view illustrating a construction of a conventional vehicle for sweeping streets. In the conventional vehicle for sweeping streets, as a driver sitting on a driver's seat drives a blower unit 8 and various driving devices by using power generated by an auxiliary engine 6, street sweeping operation is implemented. A blast capacity of the blower unit 8 is set to a high degree so that debris can be picked up irrespective of whether it is dried or wetted.
If an amount of refuse collected in a collection hopper 1 exceeds a predetermined level, hopper dumping operation is implemented in a manner such that the entire collection hopper 1 is tipped to allow contents to slide out from the collection hopper 1, by gravity, into a garbage dump. While implementing the hopper dumping operation, a door 2 provided to a rear wall of the collection hopper 1 is opened.
While the majority of refuse sucked into the collection hopper 1, which is mounted on the vehicle for sweeping streets, falls toward a bottom of the collection hopper 1, fine dust particles do not accumulate on the bottom. Even if it is possible to collect using a dust separator, the fine dust particles contained in an air stream, since a conventional dust collector generally has a large size, it is difficult to practically install in practice the large-sized dust collector on the vehicle for sweeping streets. Hence, in the conventional vehicle for sweeping streets, a filtering screen 3 is placed on a top of the collection hopper 1 so that the air stream is directed toward the blower unit 8 after passing through the filtering screen 3. Circulation of the air stream is effected by the blower unit 8.
However, a filtering effect accomplished by the filtering screen 3 is so poor that a substantial amount of fine dust particles are exhausted to the atmosphere as they are. These fine dust particles exhausted to the atmosphere cause environmental pollution and reduce visibility to thereby increase a probability of occurrence of traffic accidents.
From this point of view, street sweeping operation is implemented while water is sprayed with a view of preventing fine dust particles from rising and improving a refuse collecting efficiency. Nevertheless, in the wet type street sweeping operation, which is implemented while spraying water, since a volume of a water tank 4 is limited, it is impossible to implement the street sweeping operation for an extended period of time. And, if water filled in the water tank 4 is depleted, the vehicle for sweeping streets must necessarily return to a base place to be refilled with water and then again implement the street sweeping operation.
As can be seen from FIG. 5, due to the fact that the filtering screen 3 is placed on the top of the collection hopper 1, debris sucked into the collection hopper 1 falls toward the bottom thereof and the air stream flows toward the blower unit 8 after passing through the filtering screen 3. Of course, the collection hopper 1 and the water tank 4 are defined separately from each other.
When conducting the wet type street sweeping operation, debris, that is, refuse existing on the street is sucked into the collection hopper 1 along with water which is sprayed on the street from the water tank 4 through nozzles. Consequently, upon completion of the street sweeping operation, water as well as refuse remain in the collection hopper 1. By this fact, a weight of contents of the collection hopper 1 is increased, and water filled in the water tank 4 is quickly depleted to shorten a time of the street sweeping operation.
In the above-mentioned construction of the conventional vehicle for sweeping streets as shown in FIG. 5, the filtering screen 3 is placed on the top of the collection hopper 1, the debris pulled into the collection hopper 1 falls toward the bottom thereof, and the air stream flows toward the blower unit 8 after passing through the filtering screen 3. After being exhausted through the blower unit 8, the air stream containing a substantial amount of fine dust particles is blasted downward onto a pavement. Resultingly, even when conducting the wet type street sweeping operation while spraying water, a filtering effect accomplished by the filtering screen 3 is so insufficient that the fine dust particles contained in the air stream, which is sucked into the collection hopper 1, are exhausted to the atmosphere after passing through the filtering screen 3, to still cause environmental pollution.
Moreover, in the case that the vehicle for sweeping streets travels while not implementing the street sweeping operation, all driving force generated by a main engine of the vehicle for sweeping streets is transmitted to an axle through a differential gear. On the other hand, in the case that the vehicle for sweeping streets travels while implementing the street sweeping operation, the separately provided auxiliary engine 6 must be additionally driven, whereby a weight of the entire vehicle for sweeping streets is increased, and a manufacturing cost and fuel expenses are increased.